Harmful algae bloom found at Lake Needwood in Derwood

Officials warn public to avoid contact with water, keep pets away

Visitors to Rock Creek Regional Park are advised to stay away from the water in Lake Needwood because it contains harmful algae.

The Montgomery County Department of Parks and the Maryland Department of the Environment are suggesting that people not drink the water, avoid swimming in the lake and keep their pets away from the water because it contains strains of Microcystin, which can damage the liver and cause gastrointestinal discomfort when ingested and cause minor skin irritation upon contact.

Kelli Holsendolph, spokeswoman for the Department of Parks, said warning signs were posted around Lake Needwood in Derwood in early July and a precautionary advisory has been posted on the parks system website since July 9.

Holsendolph said Maryland Department of the Environment (MDE) officials took samples of the water in July and will return to the lake in September to check on the concentration levels of the algae.

"MDE has informed us that we can expect the problem to persist for the rest of the season," Holsendolph said.

Holsendolph said activities are continuing around the lake, including boat rentals, and visitors have not been deterred.

Doug Redmond, aquatic biologist in the Park Planning and Stewardship Division of the parks department, said he and other county and state environmentalists are uncertain how long the algae bloom has been in the lake.

"The first time we were aware of the problem was last summer," Redmond said.

He said a park patron who was an expert on blue-green algae took samples and contacted the Maryland Department of Environment.

Redmond said MDE researchers tested samples of the bloom from the lake and identified it as Microcystis, also known as cyanobacteria.

According to the Maryland Department of Natural Resources, annual late summer blooms of Microcystis have been found in the tidal freshwater portions of the Potomac River. Larger than normal blooms occurred in the upper Chesapeake Bay and its tributaries in August and September 2000. Officials have attributed the 2000 blooms to greater than normal amounts of freshwater and nutrients entering the bay.

Microcystis blooms are generally associated with warm, fresh, nutrient-enriched water. Blooms generally occur mid- to late summer and can carry into the fall.

The Department of Natural Resources states that excess nutrients and human activities can contribute to the frequency and intensity of the blooms.

Redmond said the algae have a tendency to accumulate along the edges of the leeward shore of the lake, where the water is shallow.

He said people should not worry if they have made skin contact with the water at Lake Needwood.

"The toxin is only concentrated in the algae itself, not throughout the water," Redmond said.

Redmond said he has not heard of or received any reports of people being sick from the water.

According to the Maryland Department of Health and Mental Hygiene, boiling, filtering or treating contaminated water will not make the water drinkable. Fish from the waters can be eaten, but at a minimum. The organs and skin should be removed and discarded before cooking.